Overfill of common piggyback admixture solutions.

The average final volume of 23 commonly used piggyback solutions was determined. Polyvinyl chloride (PVC) containers filled with 0.9% sodium chloride injection or 5% dextrose injection in 50 ml and 100 ml sizes were used for 20 of the piggybacks. A total of ten samples of each drug and dose were measured by draining the entire contents into a graduated cylinder and measuring the volume. The mean volumes, standard deviations, and ranges for each drug and dose were calculated. The volume found in each sample exceeded the volume in the original PVC container by at least 20% in the 50 ml size and 11% in the 100 ml size. The greatest percentage volume difference was 62% in the 50 ml size and 28% in the 100 ml size. The FasPak and the two Viaflex Plus Ready-To-Use containers, which did not require the use of the 50 and 100 ml PVC containers, had a percentage volume difference of 2.6%, 2.2%, and 3.4%, respectively. This information demonstrates the fact that the final volumes of some piggyback admixtures are significantly greater than that which may be presumed from the admixture label.